From 38c480a470d7f107945180968a5db237c671f7d0 Mon Sep 17 00:00:00 2001
From: Jacob Trimble <modmaker@google.com>
Date: Tue, 5 Dec 2017 14:52:22 -0800
Subject: [PATCH] avcodec/avcodec.h: Add encryption info side data.

This new side-data will contain info on how a packet is encrypted.
This allows the app to handle packet decryption.

Signed-off-by: Jacob Trimble <modmaker@google.com>
---
 libavcodec/Makefile          |   2 +
 libavcodec/avcodec.h         |  13 ++++++
 libavcodec/encryption_info.c |  70 +++++++++++++++++++++++++++++
 libavcodec/encryption_info.h | 105 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 190 insertions(+)
 create mode 100644 libavcodec/encryption_info.c
 create mode 100644 libavcodec/encryption_info.h

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index ab7893f560..11ad642c6c 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -10,6 +10,7 @@ HEADERS = ac3_parser.h                                                  \
           dirac.h                                                       \
           dv_profile.h                                                  \
           dxva2.h                                                       \
+          encryption_info.h                                             \
           jni.h                                                         \
           mediacodec.h                                                  \
           qsv.h                                                         \
@@ -36,6 +37,7 @@ OBJS = ac3_parser.o                                                     \
        dirac.o                                                          \
        dv_profile.o                                                     \
        encode.o                                                         \
+       encryption_info.o                                                \
        imgconvert.o                                                     \
        jni.o                                                            \
        mathtables.o                                                     \
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 5db6a81320..7a5bba2687 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -1327,6 +1327,19 @@ enum AVPacketSideDataType {
      */
     AV_PKT_DATA_A53_CC,
 
+    /**
+     * This side data is encryption "initialization data".
+     * For MP4 this is the entire 'pssh' box.
+     * For WebM this is the key ID.
+     */
+    AV_PKT_DATA_ENCRYPTION_INIT_DATA,
+
+    /**
+     * This side data contains encryption info for how to decrypt the packet.
+     * Use av_encryption_info_get to get the info out of this side data.
+     */
+    AV_PKT_DATA_ENCRYPTION_INFO,
+
     /**
      * The number of side data types.
      * This is not part of the public API/ABI in the sense that it may
diff --git a/libavcodec/encryption_info.c b/libavcodec/encryption_info.c
new file mode 100644
index 0000000000..a2c11fe213
--- /dev/null
+++ b/libavcodec/encryption_info.c
@@ -0,0 +1,70 @@
+/**
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "encryption_info.h"
+#include "libavutil/avassert.h"
+#include "libavutil/intreadwrite.h"
+
+#define FF_ENCRYPTION_INFO_EXTRA 24
+
+int av_encryption_info_get(const AVPacket* packet, AVEncryptionInfo* info) {
+    uint8_t *buffer;
+
+    buffer = av_packet_get_side_data(packet, AV_PKT_DATA_ENCRYPTION_INFO, NULL);
+    if (!buffer)
+        return 0;
+
+    info->scheme = AV_RB32(buffer);
+    info->crypt_byte_block = AV_RB32(buffer + 4);
+    info->skip_byte_block = AV_RB32(buffer + 8);
+    info->key_id_size = AV_RB32(buffer + 12);
+    info->key_id = buffer + 16;
+    info->iv_size = AV_RB32(info->key_id + info->key_id_size);
+    info->iv = info->key_id + info->key_id_size + 4;
+    info->subsample_count = AV_RB32(info->iv + info->iv_size);
+    info->subsamples = (AVSubsampleEncryptionInfo*)(info->iv + info->iv_size + 4);
+    return 1;
+}
+
+int av_encryption_info_add_side_data(AVPacket* packet, const AVEncryptionInfo* info) {
+    uint8_t *buffer;
+    size_t size;
+
+    size = FF_ENCRYPTION_INFO_EXTRA + info->key_id_size + info->iv_size +
+           (sizeof(AVSubsampleEncryptionInfo) * info->subsample_count);
+    buffer = av_packet_new_side_data(packet, AV_PKT_DATA_ENCRYPTION_INFO, size);
+    if (!buffer)
+        return AVERROR(ENOMEM);
+
+    AV_WB32(buffer,      info->scheme);
+    AV_WB32(buffer +  4, info->crypt_byte_block);
+    AV_WB32(buffer +  8, info->skip_byte_block);
+    AV_WB32(buffer + 12, info->key_id_size);
+    buffer += 16;
+    memcpy(buffer, info->key_id, info->key_id_size);
+    buffer += info->key_id_size;
+    AV_WB32(buffer, info->iv_size);
+    buffer += 4;
+    memcpy(buffer, info->iv, info->iv_size);
+    buffer += info->iv_size;
+    AV_WB32(buffer, info->subsample_count);
+    buffer += 4;
+    memcpy(buffer, info->subsamples, info->subsample_count * sizeof(AVSubsampleEncryptionInfo));
+
+    return 0;
+}
diff --git a/libavcodec/encryption_info.h b/libavcodec/encryption_info.h
new file mode 100644
index 0000000000..03052bf551
--- /dev/null
+++ b/libavcodec/encryption_info.h
@@ -0,0 +1,105 @@
+/**
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_ENCRYPTION_INFO_H
+#define AVUTIL_ENCRYPTION_INFO_H
+
+#include "avcodec.h"
+
+typedef struct AVSubsampleEncryptionInfo {
+    /** The number of bytes that are clear. */
+    unsigned int bytes_of_clear_data;
+
+    /**
+     * The number of bytes that are protected.  If using pattern encryption,
+     * the pattern applies to only the protected bytes; if not using pattern
+     * encryption, all these bytes are encrypted.
+     */
+    unsigned int bytes_of_protected_data;
+} AVSubsampleEncryptionInfo;
+
+/**
+ * This describes encryption info for a packet.  This contains frame-specific
+ * info for how to decrypt the packet before passing it to the decoder.
+ *
+ * This struct should be allocated on the stack by the app and filled by
+ * av_encryption_info_get().  The side-data contains a binary format of this
+ * struct.
+ */
+typedef struct AVEncryptionInfo {
+    /** The fourcc encryption scheme. */
+    uint32_t scheme;
+
+    /**
+     * Only used for pattern encryption.  This is the number of 16-byte blocks
+     * that are encrypted.
+     */
+    uint32_t crypt_byte_block;
+
+    /**
+     * Only used for pattern encryption.  This is the number of 16-byte blocks
+     * that are clear.
+     */
+    uint32_t skip_byte_block;
+
+    /**
+     * The ID of the key used to encrypt the packet.  This should always be
+     * 16 bytes long, but may be changed in the future.
+     */
+    uint8_t *key_id;
+    uint32_t key_id_size;
+
+    /**
+     * The initialization vector.  This may have been zero-filled to be the
+     * correct block size.  This should always be 16 bytes long, but may be
+     * changed in the future.
+     */
+    uint8_t *iv;
+    uint32_t iv_size;
+
+    /**
+     * An array of subsample encryption info specifying how parts of the sample
+     * are encrypted.  If there are no subsamples, then the whole sample is
+     * encrypted.
+     */
+    AVSubsampleEncryptionInfo* subsamples;
+    uint32_t subsample_count;
+} AVEncryptionInfo;
+
+/**
+ * Gets the encryption info out of the side data of the given packet and fills
+ * the given object with that info.  The pointers in this structure point inside
+ * the side data of this packet; this means they should NOT be freed and are
+ * only valid until the side data is freed.
+ *
+ * @param packet The packet to extract the encryption info out of.
+ * @param info The structure to fill with the encryption info.
+ *
+ * @return 1 if the packet is encrypted and the data was extracted; 0 if not.
+ */
+int av_encryption_info_get(const AVPacket* packet, AVEncryptionInfo* info);
+
+/**
+ * Adds a new side data to the given packet that holds a copy of the given
+ * encryption info.
+ *
+ * @return 0 on success, or a negative error code on error.
+ */
+int av_encryption_info_add_side_data(AVPacket* packet, const AVEncryptionInfo* info);
+
+#endif /* AVUTIL_ENCRYPTION_INFO_H */
-- 
2.15.1.620.gb9897f4670-goog

